Cuff for boiler tube assembly and method of manufacture

ABSTRACT

A system for retaining boiler tubes in an array includes a bracket having a contoured surface defining at least one channel, the channel being semi-cylindrical and defined by an elongated cross section having a rounded portion and two elongated legs extending therefrom to define a substantially U-shaped cross section, and a planar section located at a terminus of each leg. The system also comprises a plate connectable to at least one planar section of the bracket. A method of manufacturing a cuff for a boiler tube assembly includes bending a bracket having at least one channel therein, the channel being configured to receive a boiler tube of the boiler tube assembly; and machining a plate, the plate being configured and sized to be positioned over the channel.

TECHNICAL FIELD

The disclosure herein is generally directed to systems for retainingboiler tubes in place during boiler operation. More particularly, thedisclosure is directed to a cuff for retaining and maintaining boilertubes in place during high temperature and high pressure operation of aboiler. The present disclosure is further directed to a method ofmanufacturing the cuff.

BACKGROUND

A boiler is typically a closed pressure vessel defined by one or morewalls and containing a liquid that can be heated under controlledconditions. As the liquid is heated to a certain temperature, the liquidvaporizes causing an increase in pressure within the boiler. Thishigh-pressure vaporized liquid can then be used to provide work, or itcan be used as a source of heat.

Typical boilers may include a hundred or more boiler tubes arranged inparallel in a single array. Because these boiler tubes are long andrelatively thin-walled, they are subjected to significant heat stress,giving them the tendency to warp and shift out of parallel alignmentthereby reducing the uniformity and efficiency of heat transfer to theliquid in the tubes.

The industry standard for keeping the boiler tubes in alignment is aboiler tube cuff, which comprises an elongated set of mating elementsthat resemble handcuffs. This cuff is defined by semi-circular portionsthat are radially mated over a set of boiler tubes. One exemplaryembodiment of such a cuff is shown generally in FIGS. 1 and 2 and isdesignated by the reference number 10. As can be seen, the cuff 10comprises a first portion 12 that is attached to a mating second portion14 after both portions are placed such that the semi-circular portions16 accommodate the outer surfaces of the boiler tubes. After beingplaced over a set of boiler tubes in an array, the first portion 12 andthe second portion 14 are secured to one another using interlockingdevices 18 such as weldable posts or threaded bolts. In instances inwhich the boiler tubes over which the portions of the cuff 10 are warpedand misaligned, the boiler tubes are often pre-clamped in parallelbefore the cuff can be mated over them.

The mating handcuff-like devices (such as cuff 10) are typically cast,which means that the tolerances between mating portions are generallyfairly close such that contacting portions of each can suitablycoincide. Casting the first portion 12 and the second portion 14 to havesuch close tolerances generally adds substantial costs to the processesof manufacturing the cuff 10. Furthermore, the orientation of the matingportions of cuff 10 typically hinders the fastening of such portions toeach other, which may lead to deficiencies in the welds used to securethe portions together.

SUMMARY

According to one aspect described herein, there is provided a system forretaining boiler tubes in an array. This system comprises a brackethaving a contoured surface defining at least one channel, the channelbeing semi-cylindrical and defined by an elongated cross section havinga rounded portion and two elongated legs extending therefrom to define asubstantially U-shaped cross section, and a planar section located at aterminus of each leg. The system also comprises a plate connectable toat least one planar section of the bracket. The connection of the plateto the at least one planar section of the bracket closes the two legs ofthe U-shaped cross section such that a boiler tube can be retained inthe channel.

According to another aspect, there is provided a cuff for boiler tubes.This cuff comprises a bracket having a contoured surface that defines atleast one channel having open ends and an open top, the channel beingconfigured to receive a boiler tube therein. The cuff also comprises aplate located on the bracket to close the open top of the at least onechannel, thereby allowing the boiler tube to extend from at least one ofthe open ends of the channel.

According to another aspect, there is provided a method of manufacturinga cuff for a boiler tube assembly comprising a bracket fabricated fromflat stock having at least one channel therein, the at least one channelbeing defined by open ends and an open top, the channel being configuredto receive a boiler tube of the boiler tube assembly; and machining aplate, the plate being configured and sized to be positioned over theopen top of the channel. In using the cuff, the plate is attachable tothe bracket upon receiving the boiler tube in the channel.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the Figures, which illustrate exemplary embodiments,and wherein like elements are numbered alike:

FIG. 1 is a perspective view of a typical boiler tube cuff.

FIG. 2 is a perspective exploded view of the boiler tube cuff of FIG. 1.

FIG. 3 is a perspective exploded view of a U-cuff.

FIG. 4 is a perspective view of a portion of a U-cuff in which a plateis attached to a bracket using bolts and nuts.

FIG. 5 is a front view of the U-cuff having three boiler tubes insertedtherethrough.

DETAILED DESCRIPTION

Referring now to FIG. 3, a system for retaining and maintaining boilertubes in an array in a boiler during operation of the boiler comprises aplate-fabricated U-cuff, which is designated generally by the referencenumber 20 and is hereinafter referred to as “U-cuff 20.” The U-cuff 20comprises a bracket 22 having a contoured surface that defines U-shapedchannels and a plate 24 to which the bracket can be attached such thatboiler tubes are accommodated in the channels of the bracket andretained therein by the plate.

The bracket 22 is an elongated member defining a plurality of channels30 along a length L thereof. Each of the channels 30 is substantiallyU-shaped in cross section and has an open top and open ends. The U-shapeof the cross section is configured and sized to accommodate a portion ofan outer surface of a tube extending perpendicular to the direction inwhich the bracket 22 extends when the U-cuff 20 is located on the arrayof the boiler tubes (or at least one boiler tube). In particular, eachchannel 30 is a structure of a semi-cylindrical configuration having anelongated rounded portion and elongated legs such that the U-shape ofthe cross section of the channel is defined thereby, each channel beingconnected to an adjacent channel via a planar section 34 such that thebracket 22 is a series of alternating channels and planar sections.Although the U-cuff 20 is shown in FIG. 3 as including three channels30, the U-cuff is not so limited as the bracket 22 can comprise anydesired number of alternatingly positioned channels and planar sections.

The plate 24 of the U-cuff 20 comprises a planar member of substantiallythe length L (or slightly longer). A width W of the plate 24substantially corresponds to a width of the bracket 22. The plate 24comprises a plurality of weldment slots 38 located therein such thatupon assembling the plate and the bracket 22, the plate can be welded orbrazed to the bracket at the weldment slots. The connection of the plate24 to the bracket 22 is not limited to being effected using weldmentslots 38 at which welds can be made, however, as either the bracket orthe plate may include tangs or posts that extend through openings in theother of the plate or the bracket to facilitate the joining of thebracket and the plate by welding.

The joining of the bracket 22 and the plate 24 is also not limited towelding or brazing, as other methods of attaching the bracket to theplate can be employed. Referring now to FIG. 4, the bracket 22 can beattached to the plate 24 via the use of threaded bolts 138. The threadedbolts 138 may be integral with the planar sections 34 on the bracket 22,or they may be inserted through openings in both the planar sections andthe bracket. In either embodiment, nuts 140 are located on the threadedbolts 138 and tightened to fasten the plate to the bracket. Othermethods of securing the plate 24 to the bracket 22 include, but are notlimited to, pins, rivets, and any other suitable device inserted throughthe planar sections 34 and the plate.

Referring now to FIG. 5, the U-cuff 20 is shown with a boiler tube 40located in a channel 30. The plate 24 is also shown being mounted on thebracket 22, thereby holding the boiler tube 40 in the U-cuff 20. Aportion of an inner surface of each channel 30 of the bracket 22 isconfigured to correspond to a portion of an outer surface of each boilertube 40 located therein. A depth D of each channel 30 substantiallycorresponds to the diameter of the boiler tube 40. In doing so, a boilertube 40 is retained in the U-cuff 20 by being held by the inner surfaceof the rounded portion and the inner surfaces of the legs of the channel30 and the surface of the plate 24 that faces the bracket 22. Tolerancesbetween the outer surface of the boiler tube 40 and the surfaces of thechannel 30 and/or the plate 24 can be introduced as desired.

Materials from which the U-cuff 20 may be fabricated include, but arenot limited to, alloys of nickel, chromium, and iron and alloys ofchromium and nickel. One exemplary Ni—Cr—Fe alloy is Alloy 601, alsoknown as 60Ni-23Cr—Fe. Alloy 601 is especially desirable for the bracket22 because it is highly resistant to oxidation up to about 1,250 degreesC. and can weather severe conditions such as cyclical heating andcooling in a boiler environment. One exemplary Cr—Ni alloy is Alloy 309(austenitic stainless steel), which is 23Cr-12Ni. Alloy 309 isespecially desirable for the plate 24 as it is highly weldable andexhibits high resistance to aqueous corrosion.

Although the bracket 22 as shown in FIG. 3 has three channels 30 and thebracket 22 as shown in FIG. 5 has seven channels 30, the U-cuff 20 isnot limited in either of these regards as any suitable number ofchannels may be incorporated into the bracket to accommodate any desirednumber of boiler tubes 40.

The U-cuff 20 can be produced at far less cost than cast cuff alignmentdevices and is therefore less expensive per boiler tube aligned. Morespecifically, by manufacturing the U-cuff 20 by a method of bending thebracket 22 and machining the plate 24 from flat stock, the cost ofproducing the U-cuff 20 is substantially reduced as compared to cuffscomprising two or more mating portions that are cast. Furthermore,because the plate 24 is manufactured from a material that is highlyweldable as compared to cast materials, the welding costs associatedwith installing a boiler tube assembly using the U-cuff 20 are furtherreduced. By reducing the overall cost of the product, bids for theinstallation of boiler tube assemblies in boilers can become morecompetitive in the boiler industry.

Although this invention has been shown and described with respect to thedetailed embodiments thereof, it will be understood by those of skill inthe art that various changes may be made and equivalents may besubstituted for elements thereof without departing from the scope of theinvention. In addition, modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodimentsdisclosed in the above description, but that the invention will includeall embodiments falling within the scope of the appended claims.

1. A system for retaining boiler tubes in an array, the systemcomprising: a bracket comprising, a contoured surface defining at leastone channel, the channel being semi-cylindrical and defined by anelongated rounded portion and two elongated legs extending therefrom todefine a substantially U-shaped cross section, and a planar sectionlocated at a terminus of each leg; and a plate connectable to at leastone planar section of the bracket; wherein the connection of the plateto the at least one planar section of the bracket closes the two legs ofthe U-shaped cross section; and wherein a boiler tube can be retained inthe channel.
 2. The system of claim 1, wherein the plate includes atleast one weldment slot located therein, the at least one weldment slotbeing configured to correspond with at least one planar section of thebracket.
 3. The system of claim 2, wherein the plate is welded to the atleast one planar section of the bracket at the at least one weldmentslot.
 4. The system of claim 1, wherein the plate is connectable to theat least one planar section of the bracket using a bolt and nut.
 5. Thesystem of claim 1, wherein the bracket is fabricated from a Ni—Cr—Fealloy.
 6. The system of claim 5, wherein the Ni—Cr—Fe alloy is Alloy601.
 7. The system of claim 1, wherein the plate is fabricated from astainless steel alloy.
 8. The system of claim 7, wherein the stainlesssteel alloy is Alloy
 309. 9. A cuff for boiler tubes, the cuffcomprising: a bracket having a contoured surface that defines at leastone channel having open ends and an open top, the channel beingconfigured to receive a boiler tube therein; and a plate located on thebracket to close the open top of the at least one channel, therebyallowing the boiler tube to extend from at least one of the open ends ofthe channel.
 10. The cuff of claim 9, further comprising at least oneopening on the plate at which the bracket can be attached to the plate.11. The cuff of claim 10, wherein the opening on the plate is a weldmentslot at which a weld can be made to attach the bracket to the plate. 12.The cuff of claim 9, wherein the bracket is a Ni—Cr—Fe alloy.
 13. Thecuff of claim 9, wherein the plate is a stainless steel alloy.
 14. Amethod of manufacturing a cuff for a boiler tube assembly, the methodcomprising the steps of: bending a bracket having at least one channeltherein, the at least one channel being defined by open ends and an opentop, the channel being configured to receive a boiler tube of the boilertube assembly therein; and machining a plate, the plate being configuredand sized to be positioned over the open top of the channel; wherein theplate is attachable to the bracket upon receiving the boiler tube in thechannel.
 15. The method of claim 14, further comprising welding thebracket to the plate.
 16. The method of claim 14, wherein the bracket isbent from a Ni—Cr—Fe alloy flat stock.
 17. The method of claim 14,wherein the plate is machined from a stainless steel alloy flat stock.